This invention relates to an apparatus and method for separating fibers from a solid sample which comprises a solid material having such fibers embedded therein. Such a solid sample is commonly characterized as a "composite".
Fiber content plays a major role in determining the structural characteristics of composites. Therefore, it is frequently desirable to determine the fiber content of a composite which is being manufactured and/or tested. In order to determine the fiber content of such a composite, it is necessary to separate the fibers from a composite sample for weighing. Heretofore, such separation techniques have been labor intensive and potentially hazardous to laboratory personnel.
By way of example, carbon fibers are typically separated from poly(phenylene sulfide) based composites by utilizing nitric acid to digest or dissolve the solid poly(phenylene sulfide) resin to liquid form. According to such a technique, a quantity of nitric acid is poured into a beaker, the beaker placed on a hot plate, and the acid's temperature raised to about 100.degree. C. At such time a composite sample is placed in the acid and allowed to digest for a predetermined period of time, after which the beaker's liquid contents are poured into a buchner funnel (which contains an appropriate filter) while carefully holding back the carbon fibers with a glass rod. Additional nitric acid is then added to the beaker and the beaker is returned to the hot plate for a second digestion period to dissolve any residual resin. The contents of the beaker are again poured into the buchner funnel, this time along with the carbon fibers. The filter in the buchner funnel allows passage of liquids therethrough but retains the carbon fibers. All of the above-described steps are performed manually so as to risk exposure to hot acid, acid fumes, and airborne fibers.